Apparatus for processing materials

ABSTRACT

The present invention relates to an apparatus for processing materials, a process for mixing, finishing and de-volatizing polyamide to make 66 nylon and the 66 nylon made by this process. The apparatus comprises an agitator section having an outlet adjacent the bottom thereof; a transfer screw disposed adjacent the outlet of the agitator section; a spiral ribbon extending upwardly from the transfer screw; a ring disposed vertically above the spiral ribbon, at least one baffle disposed vertically above the spiral ribbon and connected to the ring and a wall-wiping spur connected to the ring. Preferably, the apparatus has two baffles--an upper one for pumping the material downwardly and a lower one for pumping the material upwardly. The diameter of each baffle is preferably about 80% of the diameter of the agitator section.

BACKGROUND OF THE INVENTION

1. Field of The Invention

The present invention relates to an apparatus for processing at leastone material, and is particularly suited for mixing, finishing andde-volatizing polymers.

2. Description of the Related Art

The commercial preparation of most linear condensation polymers, such aspolyamides or polyesters, typically involves heating monomeric startingmaterials to cause progressive condensation of the polymers. Thisprocess is usually carried out in several stages, with the intermediateformation of low-molecular weight, low viscosity polymeric liquid by theremoval of volatiles. The low-molecular weight, low-viscosity polymericliquid then passes through a finishing zone which is controlled atvarious vacuum and residence times and temperatures to allow the polymerto reach the desired final molecular weight and viscosity.

Undesirable side reactions, such as thermal degradation anddiscoloration of polymers in polymerization equipment can occur in thepreparation of polymers. Such side reactions have long been recognizedin the field of polymer processing. Finishers such as those described inU.S. Pat. No. 3,361,537 to Ferrante and U.S. Pat. No. 4,134,736 toHammond have produced polymers of uniform viscosity, with less thermaldegradation, discoloration and gel build-up than finishers which hadbeen previously available.

Separators have also been used in the art of polymer processing forproducing polymers of lower molecular weight than finishers produce.Separators are devices which operate at one atmosphere, while finishersoperate at one atmosphere or lower with vacuum. It is known to operate apolymerization device as both a separator and a finisher, as exemplifedby U.S. Pat. No. 3,717,330 to Pinney. It is also known in the art toprovide a separator which comprises a spiral ribbon extending upwardlyfrom a transfer screw and a ring disposed above the spiral ribbon, asdescribed in U.S. Pat. No. 3,087,435 to Boucher, with baffles which areconnected to a plurality of spokes attached to the transfer screw anddisposed below the ring. These baffles have a helical shape and haveholes formed therein, and always pump downwardly. The use of a baffle ina reactor, or finisher, is also disclosed in U.S. Pat. No. 4,460,278 toMatsubara et al., U.S. Pat. No. 4,007,016 to Weber, U.S. Pat. No.3,822,999 to Pope and U.S. Pat. No. 2,804,379 to Wistrich et al.

A major design consideration in polymerizing equipment is flow pattern,which influences final polymer color and quality. Areas of stagnation orchanneling are known flow problems and are indicative of non-ideal flow.Ideally, the polymer should flow through a series of several well-mixedstages throughout its residence time in the equipment, while maintainingplug-flow, i.e., substantially uniform liquid flow velocities of all thepolymer in a given transverse cross-section of the equipment. Theseparators and finishers described above do not provide uniform mixingand ideal flow conditions. Also, these finishers and separators exhibitsignificant gel formation above the surface of the polymer and thermaldegradation of the polymer.

As demand increases for polymers of higher molecular weight and for moreflexible polymer producing operations with higher throughputs, neitherthe separators nor the finishers as described above are able to producedesired polymers. With such desired higher molecular-weight polymers andhigher throughputs, gel, color and other polymer quality specificationssuch as thermal degradation index and oxidative degradation index becomean increasing problem. To achieve the increased throughput, largerfinishers or separators are required. To achieve higher molecularweight, higher viscosity polymer must be processed. The larger finishersor separators and the higher-viscosity polymers require increased power,which results in increased energy input. This increased energyrequirement is obviously undesirable from an economic standpoint, andhas the additional disadvantages of requiring stronger structures forthe finishers or separators and overheating the polymer in the finisher,ultimately resulting in a thermally degraded, inferior product.

SUMMARY OF THE INVENTION

The present invention solves the problems associated with the prior artby providing an apparatus for processing at least one material which isparticularly useful as a mixer for mixing polymer, and/or as a finisherfor preparing high molecular weight, high-viscosity polymer and/or as ade-volatizer for removing volatiles from the polymer.

The present invention also solves the problems associated with the priorart by providing an apparatus which minimizes the energy input and costrequired to operate the apparatus, and which has maximized mechanicalstrength.

The present invention also solves the problems associated with the priorart by providing an apparatus which reduces gel formation.

The present invention also solves the problems associated with the priorart by providing an apparatus which provides uniform mixing and preventsexcessive channeling and stagnation of the material.

In order to achieve the foregoing solutions, in accordance with thepresent invention, there is provided an apparatus for processing atleast one material. The apparatus comprises an agitator section havingan outlet adjacent the bottom thereof; a transfer screw disposedadjacent the outlet of the agitator section; a spiral ribbon extendingupwardly from the transfer screw; a ring disposed vertically above thespiral ribbon; and at least one baffle disposed vertically above thespiral ribbon and connected to the ring.

Further in accordance with the present invention, it is preferable thatthe at least one baffle comprises a first baffle for pumping thematerial downwardly, and a second baffle disposed below the first bafflefor pumping the material upwardly. It is further preferable that thediameter of the first and second baffles is about 80% the diameter ofthe agitator section.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate the presently preferredembodiments of the invention and, together with the general descriptiongiven above and the detailed description of the preferred embodimentsgiven below, serve to explain the principles of the invention.

FIG. 1 is an elevational view of the apparatus of the present invention.

FIG. 2 is a cut away, elevational view of the apparatus of FIG. 1,showing the agitator section and the top of the transfer screw.

FIG. 3 is a cross-sectional view, taken across lines 3--3 of FIG. 2, ofthe ring of the apparatus of the present invention.

FIG. 4 is a plan view showing a preferred design of the top baffle ofthe present invention.

FIG. 5 is a cross-sectional view, taken across lines 5--5 of FIG. 2,showing the diagonal supports of the apparatus having a generallytear-drop shape according to one embodiment of the present invention.

FIG. 6 is a cross-sectional view, taken across lines 6--6 of FIG. 2,showing a major spoke of the apparatus having a generally trapezoidalshape according to a further embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention as illustrated in the accompanyingdrawings.

In accordance with the present invention, there is provided an apparatusfor processing at least one material. The apparatus of the presentinvention is shown generally at 10 in FIGS. 1 and 2. "Processing" maymean mixing, or alternatively, or in addition, finishing, (i.e.,producing a reaction and converting a low viscosity material to a highviscosity material), or alternatively, or in addition, de-volatizing(i.e., stripping out gas) in a material. The apparatus of the presentinvention may process either one material or a mixture of materials, atleast one of which is a liquid. In general, the apparatus of the presentinvention is ideal for handling a foamy material. Materials suitable formixing and finishing with the apparatus of the present invention include6 nylon, whereby water and caprolactan are removed, 6, 6 nylon, wherebywater is removed, polyarylates, whereby acetic acid and phenol isremoved and polyesters, where glycols are removed. A material suitablefor mixing and de-volatizing with the apparatus of the present inventionincludes polyethylene, whereby ethylene gas is removed.

The apparatus of the present invention comprises an upright tubularagitator section 12 as shown in FIGS. 1 and 2 having an outlet 14adjacent the conically-shaped bottom of the agitator section. Materialenters the apparatus at the top thereof, usually through a centralnozzle 16 as shown in FIG. 1, as indicated by the arrow going into thenozzle. Alternately, several entry nozzles may be employed. When theapparatus of the present invention is used as a finisher or ade-volatizer, by-product gas from the nozzle or from the material flowsupwardly and out through a vent 18. A transfer screw 20 is disposedadjacent the outlet of the agitator section as shown in FIG. 1. Transferscrew 20 extends through the bottom of the agitator section andterminates in an auger screw element 21 as shown in FIG. 2, which mayhave one or more turns. The purpose of the transfer screw is to removethe material from the apparatus and transport it to a downstreamtransfer line 22 as indicated by the arrow in line 22 and then to a gearpump, not shown. Further downstream operations, such as spinning andcasting, may then be performed on the material. Agitator section 12 hasan agitator 13 as shown by the dashed lines in FIG. 1 which extendsupwardly from the transfer screw and is driven thereby. The agitatorsection is joined to the transfer screw by a key and screw joint (notshown), allowing ease of disassembly for routine maintenance. It is ofcourse within the scope of the present invention to use other attachmentmechanisms between the agitator section and the transfer screw.

A spiral ribbon 24 extends upwardly from the transfer screw as shown inFIG. 2. Spiral ribbon 24 mixes the material in the lower portion of theagitator section. It blends out any non-uniformities generated byupstream process upsets, so that very uniform material is fed todownstream operations. The spiral ribbon also wipes the walls of theagitator section, thus preventing gel build-up. Furthermore, thegeometry of the spiral ribbon within the agitator section encouragesdownward pumping of the material, further enhancing the gel-inhibitingcharacteristics of the ribbon and thus the quality of the material. Forvery large apparatus, for example when the agitator section diameter isgreater than 50 inches, the horsepower requirement to rotate the ribbonbecomes unreasonably high. This excessive horsepower requirement causesthe temperature of the material to increase, resulting in thermaldegradation. Therefore, for large apparatus, it is preferred to limitthe spiral ribbon to be disposed below the 50-inch diameter portion ofthe agitator section. For small apparatus, where the horsepowerrequirement is less of a concern, it may be preferred to allow theribbon to extend through the entire material zone in the agitatorsection.

A ring 26 is disposed vertically above the spiral ribbon. The ringprovides mechanical integrity to the entire agitator section. Thepreferred cross-section of the ring is wedge-shaped on the top, as canbe seen from FIG. 3. The advantage of providing a wedge-shaped crosssection is that the material flows over the wedge and does not stagnatethere, which would result in gel formation.

A plurality of diagonal supports 30 as shown in FIG. 2 connect thespiral ribbon to the ring. The supports are welded to the ribbon and thering, although other attachment methods may be chosen. The diagonalsupports may have a generally tear-drop shape, as shown in FIG. 5. Atear-drop shape enables the laminar flow of the material to flow in astream line with respect to the walls of the agitator section. Thiseliminates stagnant or void zones, which lead to gel formation. Thediagonal supports are provided for additional mechanical strength toavoid twisting and distortion of the agitator section. For low-viscosityapplications, these diagonal supports may be unnecessary. However, whenused, the diagonal supports must be located in positions that will notcontribute to gel build-up or cause improper flow patterns, such aschanneling.

The apparatus of the present invention further comprises at least onebaffle disposed vertically above the spiral ribbon and connected to thering. The apparatus further includes a plurality of baffle supportmembers 38 for connecting the baffle to the ring. Each baffle is bolteda baffle support member. The at least one baffle comprises a first, orupper, baffle 32a for pumping the low-viscosity material downwardly.Upper baffle 32a serves several purposes. Incoming material drops downand encounters baffle 32a and is radially distributed, resulting in animproved flow pattern within the apparatus. Without a baffle, thematerial would tend to channel down through the material in the agitatorsection, the outer region would stagnate and severe degradation wouldresult. In addition, gel stalactites often form on the apparatus. As thestalactites become heavier, they eventually drop off, into the material.The upper baffle catches these stalactites and acts as a filter, notallowing them to pass into the downstream processes, which causes severeproblems. In polymerizing processes that cause foam formation, such asnylon polymerization, the upper baffle is designed to pump downwardlyand thereby serves the purpose of pumping the contents of the apparatusdownwardly and compressing the foam formed during the polymericreaction.

The at least one baffle may further comprise at least one second, orlower, baffle 32b, as shown in FIG. 2 by dashed lines, for pumping thematerial upwardly. Inclusion of lower baffle 32b is preferred, but isnot an essential feature of the invention. In contrast to the upperbaffle 32a, the helical geometry of the lower baffle causes lower baffle32a to pump material upwardly, which enhances flow pattern and residencetime distribution. In a preferred embodiment, the lower baffle islocated eight to twelve inches below the upper baffle. Although only twobaffles are illustrated, additional lower baffles for pumping thematerial upwardly may be added as the apparatus height is increased. Forinstance, if more than two baffles are used with the present invention,all the lower baffles pump would upwardly and the middle baffle would beoriented 180° from the top baffle. In this case, the upper baffle, suchas baffle 32a, would be bolted to the lower baffle, such as 32b.

The diameter of the first and second baffles is in the range of about50% to 99% of the diameter of the agitator section, measured at theheight of the baffle. The upper value for the baffle diameter is limitedonly by the necessary clearance between the baffle and the wall of theagitator section. Preferably, the diameter of the baffle is preferablyabout 80% of the diameter of the agitator section, measured at theheight of the baffle.

The static level of the material is horizontal at zero rotational speed.Upon rotation the surface of the material assumes the shape of aparabola, in that the material at the wall above the agitator sectionclimbs several inches up the wall and the material at the center of theagitator section drops several inches. In a preferred embodiment, thetop of the upper baffle is ideally located four to five inches below thestatic level of the material to prevent the center of the baffle frombecoming dry. If this occurs, then gel will form in the dry area, due tostagnation and degradation.

Each baffle is made of a corrosion-resistant material, such as metal. Ithas been found that any solid baffle, made of any material, will causeflow stagnation and polymer degradation. Therefore, each baffle has aplurality of holes formed therein in order to reduce the surface area ofthe baffle which is exposed to the material being processed. As shown inthe top baffle of FIG. 4, a plurality of holes 34a are formed therein,it being understood that similar holes, although not shown, are formedin the bottom baffle. The formation of holes in the baffle preventsstagnation, resulting in better quality material (i.e., one withvirtually no gel formation) to a much greater degree than what could beachieved by a baffle with no holes formed therein. The formation ofholes in the baffle also creates better flow patterns, i.e., there isvery effective pumping of the material across the surface of the baffle,thereby also preventing gel formation. Enough holes may be formed in thebaffle so that the material from which the baffle is made may compriseonly 5% of its surface area. The holes may be round, or preferably,rectangular as shown in FIG. 4. It has been found that thisconfiguration of rectangular holes as shown in FIG. 4 producessignificant lowering of gel deposition on the baffle.

A spur 36 is connected to the ring as shown in FIG. 2. The purpose ofspur 36 is to wipe the walls of the agitator section to improve flowpatterns by reducing the tendency for the material to create a beachline of gel on the walls above the material surface. Also, bypositioning the spur opposite the cut in the baffle as shown in FIG. 2,it provides additional radial mixing and decreases the tendency forstagnation to occur. By canting the spur forward, it can also serve topump material downwardly. The spur is optional, and may not be requiredin some polymer applications. However, in the case of the presentinvention where two or more baffles are used, the spur is necessary toprovide radial mixing at the surface of the material, so that thecentral feed of the material does not channel down through theapparatus. Preferably, the top of the spur is below the surface of thematerial, preferably about 1/2 inch, to avoid protrusion above the levelof the material, which would provide a dry region on the spur where gelwould form. Preferably, the spur is trapezoidal in shape. A trapezoidalshape enables the laminar flow of the material to flow in a stream linewith respect to the walls of the agitator section. This eliminatesstagnant or void zones, which leads to gel. Although more than one spurmay be provided, a single spur has the advantage of minimal powerrequirements, since spur horsepower is directly proportional to thenumber of spurs used. The spur may be unbolted from the ring andinterchanged with a spur of a different height, so that its height canbe easily changed if a change in the level of the material is required.Throughput changes require different hold-up volumes, which are achievedby changing the level of material in the agitator section. Hold-upvolume can be adjusted by changing the height of the spur and the numberand position of the baffles, which can be changed by unbolting them fromthe baffle supports as noted above.

Each baffle is cut along a radial line and extends above and below ahorizontal plane at an angle, Θ/2, so that it has a helical shape asshown in FIG. 2. Various pitches, either right or left handed, may bechosen for the baffles. As shown in particular in FIGS. 2 and 4, thefirst, or top baffle, is cut along a radial line 40a intersecting thevertical center line of the spur. The second, or bottom, baffle is cutalong a radial line 40b which intersects the top end point of the spiralribbon. The helical shape of the baffles promotes proper flow patterns,by avoiding excessive channeling at the center of the baffle. Inaddition, the orientation of the helical baffles with respect to eachother, when more than one baffle is used, creates compartments ofwell-mixed flow which move downwardly through the apparatus.

As shown in FIG. 2 in particular, a plurality of radially spaced majorspokes 42 extend between the ring and the transfer screw. Thisconfiguration of the major spokes is optimal for high viscositymaterials. The major spokes are positioned very close to the wall ofagitator section 12 to provide wall wiping and reduction of gel at thewall and the supports. The clearance between the major spokes and theagitator section wall can be varied, with the ideal clearance being lessthan one inch for the preferred embodiment. As can be seen in FIG. 6,the wall side of the major spokes has the same contour as the agitatorsection wall to avoid gel and reduce inward mechanical pressure whichwould produce stress on the supports, resulting in failure. It ispreferred to use the minimum number of major spokes necessary to achievethe required mechanical stability for a particular application in orderto minimize power requirements.

The apparatus of the present invention also includes a plurality ofradially spaced minor spokes 44 which extend between the spiral ribbonand the transfer screw. As shown in FIG. 2 in particular, the major andthe minor spokes are disposed on the outside of the spiral ribbon. Itshould be noted that the baffle may alternatively be connected to thespokes below the ring. The major and the minor spokes preferably have atrapezoidal shape, a major spoke being shown in cross-section in FIG. 6.As noted above, a trapezoidal shape enables the laminar flow of thematerial to flow in a stream line with respect to the walls of theagitator section, thereby eliminating stagnant or void zones, which leadto gel. For applications using materials not subject to gel formation,alternatively, the major and minor spokes may have a tear-drop shape,similar to the tear-drop shape for the diagonal supports as shown inFIG. 4. Since tear-drop shaped spokes cost less to manufacture thantrapezoidal spokes, they are preferred for such applications.

The total number of major and minor spokes is strictly a function of theviscosity of the material being processed. For processing materials withlow viscosities, say below 50 poise, the apparatus of the presentinvention needs only three spokes. As the viscosity of the material andthe size of the apparatus increases, more spokes are needed. Preferably,the total number of major and minor spokes is six when processingmaterials with relatively high viscosities.

Preferably, the major and the minor spokes are made of acorrosion-resistant material, such as 300 or 400 series stainless steel.In situations were lower viscosity materials are processed, the entireapparatus may be made from 300 or 400 series stainless steel. However,in situations where higher viscosity materials are processed, the majorand minor spokes may be made of 17-4 pH stainless steel, which is anextremely high strength, corrosion resistant material, while the rest ofthe apparatus can still be made of 300 or 400 series stainless steel.

The apparatus of the present invention may further comprise at least onefillet for filling in an open space in the apparatus with metal, therebypreventing cavitation. A plurality of fillets 46 is shown underneath thespiral ribbon at the joint of the spokes in FIG. 2, while a plurality offillets 48 is shown below the ring in FIG. 2. Alternatively, or inaddition, a fillet may be provided at each location of where the spokeis welded into the ring.

In operation, the material flow through nozzle 16, agitator section 12,transfer screw 20 and out line 22. The apparatus of the presentinvention produces a series of vertically segmented zones in thematerial as it flow through the apparatus. The upper vertical zonesformed by the baffle allow lower viscosity to be maintained in the upperzones of the apparatus, and higher viscosities to be maintained in thelower zones, near the spiral ribbon. This flow distribution has theadvantages of better quality product, i.e., one with virtually no gel ordiscoloration, greater reaction efficiency (when the apparatus is usedas a finisher) and reduced power consumption. Lower power consumptionresults in lower heat rise in the material and subsequent lower thermaldegradation. Also, it has been found that the residence timedistribution in the apparatus of the present invention is superior tofinishers of the prior art, thus reducing channeling, stagation and gelformation.

A preferred use for the apparatus of the present invention is as amixer, finisher and de-volatizer in a continuous process for thepreparation of a synthetic, linear, fiber-forming polyamide by the meltpolymerization of an aqueous solution of a polyamide-forming salt of analiphatic diamine and a dicarboxylic acid. Thus, in accordance with thepresent invention, there is provided an improvement in a continuousprocess for preparing a synthetic, linear, fiber-forming polyamide bythe melt polymerization of an aqueous solution of a polyamide-formingsalt of an aliphatic diamine and a dicarboxylic acid. The improvementcomprises the step of processing the polyamide in an apparatus asdescribed above comprising a transfer screw disposed adjacent an outletof an agitator section, a spiral ribbon extending upwardly from thetransfer screw, a ring disposed vertically above the spiral ribbon andat least one baffle disposed vertically above the spiral ribbon andconnected to the ring, to thereby mix, finish and de-volatize thepolyamide. The processing step includes the sub-step of vacuum finishingand separating the polyamide in one stage. Most preferred is the use ofthe apparatus of the present invention as a mixer, finisher andde-volatizer in a continuous process for the preparation ofpolyhexamethylene adipamide (66 nylon) from an aqueous solution of ahexamethylenediammonium adipate (66 nylon salt). Therefore, in thepreferred process of the present invention, the synthetic, linear,fiber-forming polyamide is polyhexamethylene adipamide. The result ispolyhexamethylene adipamide made by the process of the presentinvention.

TEST METHODS

The following test methods were used to evaluate the 66 nylon finishedby finishing apparatus of the prior art and the apparatus of the presentinvention as described in the Examples below.

Thermal degradation index (TDI) is a measurement that correlates with apolymer's thermal history. A lower TDI indicates less severe temperaturehistory during manufacture. It is determined by measuring the opticalabsorbance of a 1% (by weight) solution of the polymer in 90% formicacid at 292 nm.

Oxidative degradation index (ODI) is a measurement that correlates witha polymer's exposure to oxidating conditions during its high temperaturemanufacture. A lower ODI indicates less severe oxidative degradationduring manufacture. It is determined by measuring the optical absorbanceof a 1% (by weight) solution of the polymer in 90% formic acid at 260nm.

Relative viscosity refers to the ratio of solution and solventviscosities measured in a capillary viscometer at 25° C. The solvent isformic acid containing 10% by weight water. The solution is 8.4% byweight polyamide polymer dissolved in the solvent.

GENERAL PROCEDURES

A typical reaction system for the preparation of 66 nylon, such as thosedescribed in U.S. Pat. No. 3,113,843 to Li and U.S. Pat. No. 3,900,450to Jaswal et al. and used in the Examples as described below, comprises,sequentially, a reactor stage, a flasher stage, a steam/polymerseparator stage and a vacuum finishing stage. The reaction system may bepreceded by an evaporator to adjust the concentration of the 66 nylonsalt solution prior to the reactor. The apparatus of the presentinvention as used in Example 3 carried out both the steam/polymerseparation, such as in separator 14 of Li, and the vacuum finishing,such as in finisher 16 of Li.

In a typical 66 nylon process, an aqueous solution ofhexamethylenediammonium adipate (6,6 nylon salt) varies between 35 and65% by weight. Strength may be adjusted in the optional evaporatorupstream of the reactor stage. The effluent from the flasher stage(which is also referred to as the secondary reactor) comprises polyamidepre-polymer, typically 9-20 RV (relative viscosity). This stream is fedto a finishing apparatus. Control variables in the finishing apparatusare temperature, pressure and hold-up volume. These control variablescan be varied such that a final polymer of the desired RV, typically inthe range of 30 to 100, is obtained. Temperature in the finishingapparatus is maintained in the range of 270° to 290° C. Pressure ismaintained at 250 to 640 millibars. Hold-up volumes are approximately 20to 40 minutes.

The process and the product of the present invention will be clarifiedby the following Examples, which are intended to be purely exemplary ofthe invention.

In Examples 1-3 below, three different reaction systems for thepreparation of polyhexamethylene adipadipamide (66 nylon) usingfinishers are compared. One continuous process for preparing 66 nylon isdisclosed in U.S. Pat. No. 3,947,424 to Tomek. This process was carriedout in an apparatus for separating a vapor from a viscous materialdisclosed in U.S. Pat. No. 3,113,843 to Li, as described below inComparative Example 1. Another continuous process for preparing 66 nylonwas carried out in a continuous polymerization system as disclosed inU.S. Pat. No. 3,900,450 to Jaswal et al. Comparative Example 2 used thecontinuous polymerization system, including rectifying zone 10, firstreaction zone 12 of FIG. 1 and flasher 53 of FIG. 3 of Jaswal et al. anda combined separator/finisher such as that shown in U.S. Pat. No.3,717,330 to Pinney. Example 3 used the continuous polymerizationsystem, including rectifying zone 10, first reacting zone 12 of FIG. 1of Jaswal et al. and a flashing reactor such as reactor 12 of Li insteadof flasher 53 of FIG. 3 of Jaswal et al. and the apparatus of thepresent invention in place of finisher 64 of Jaswal et al. The apparatusof the present invention was used to mix, finish and de-volatize.

Comparative Example 1

An approximately 50% by weight aqueous solution (as adjusted in anevaporator) of hexamethylenediammonium adipate (6,6 nylon salt), apolyamide-forming salt solution, was fed to a conventional continuouspolymerization process similar to the type disclosed in Tomek, exceptthat no additives were employed. The equipment configuration of thepolymerization system was as described above. Conditions were adjustedsuch that final polymer exhibited a relative viscosity (RV) ofapproximately 50. Quality parameters are shown below in Table 1.

Comparative Example 2

An approximately 50% by weight aqueous solution ofhexamethylenediammonium adipate (6,6 nylon salt), a polyamide-formingsalt solution was fed to a conventional continuous polymerizationprocess similar to the type disclosed in Tomek, except that no additiveswere added. The equipment configuration of the polymerization system wasas described above. Conditions were adjusted such that final polymerexhibited a relative viscosity (RV) of approximately 50. Qualityparameters are shown below in Table 1.

Example 3

An approximately 63% by weight aqueous solution ofhexamethylenediammonium adipate (6,6 nylon salt), a polyamide-formingsalt solution was fed to a conventional continuous polymerizationprocess similar to the type disclosed Tomek, except no additives wereused. The equipment configuration of the polymerization system was asdescribed above. Conditions were adjusted such that final polymerexhibited a relative viscosity (RV) of approximately 50. Temperature inthe apparatus of the present invention was maintained at a temperaturein the range of 270° to 290° C. Pressure was maintained at 250millibars. Residence time in the apparatus was approximately 30 minutes.The improvements in the 66 nylon product made by the process of thepresent invention are shown below in Table 1.

                  TABLE 1                                                         ______________________________________                                                      RV       TDI    ODI                                             ______________________________________                                        Comparative Example 1                                                                         51.1       0.33   0.31                                        Comparative Example 2                                                                         51.7       0.37   0.30                                        Example 3       50.9       0.32   0.24                                        ______________________________________                                    

As can be seen from Table 1, when the process of the present inventionwas carried out (i.e., using the apparatus of the present invention),the resulting polymer showed decreased degradation when compared topolymer processed by the finishing apparatus of the prior art. Thisimprovement relates both to thermal degradation, which leads to gelformation (cross linking) and to thermally-induced oxidativedegradation, which leads to discoloration.

Additional advantages and modifications will readily occur to thoseskilled in the art. The invention in its broader aspects is, therefore,not limited to the specific details, representative apparatus andillustrative Examples shown and described. Accordingly, departures maybe made from such details without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. An apparatus for processing at least onematerial, comprising:(a) an agitator section having an outlet adjacentthe bottom thereof; (b) a transfer screw attached to the agitatorsection; (c) a spiral ribbon extending upwardly from the transfer screwend attached thereto; (d) a ring disposed vertically above the spiralribbon; and (e) means for pumping the material baffle disposedvertically above the spiral ribbon and connected to the ring.
 2. Theapparatus of claim 1, wherein the diameter of the baffle means is about80% of the diameter of the agitator section at the height of the bafflemeans.
 3. The apparatus of claim 1, wherein the baffle means comprises afirst baffle for pumping the material downwardly.
 4. The apparatus ofclaim 3, wherein the baffle means further comprises at least one secondbaffle disposed below the first baffle for pumping the materialupwardly.
 5. The apparatus of one of claims 1 or 4, further including aspur connected to the ring for wiping the walls of the agitator section.6. The apparatus of claim 5, wherein the first baffle is cut to form ahelix along a radial line intersecting the vertical cester line of thespur and the second baffle is cut along a radial line intersecting thetop end point of the spiral ribbon.
 7. The apparatus of claim 1, whereinthe baffle means has a plurality of holes formed therein.
 8. Theapparatus of claim 7, wherein the holes are rectangular.
 9. Theapparatus of claim 1, further including a plurality of baffle supportmembers for connecting the baffle means to the ring.
 10. The apparatusof claim 1, further including a plurality of diagonal supports forconnecting the spiral ribbon to the ring.
 11. The apparatus of claim 10,wherein the diagonal supports have a tear-drop shape.
 12. The apparatusof claim 1, further including a plurality of radially spaced majorspokes extending between the ring and the transfer screw.
 13. Theapparatus of claim 12, further including a plurality of radially spacedminor spokes extending between the spiral ribbon and the transfer screw.14. The apparatus of claim 13, wherein the major and the minor spokeshave a trapezoidal shape.
 15. The apparatus of claim 13, wherein themajor and the minor spokes are disposed on the outside of the spiralribbon.
 16. The apparatus of claim 13, wherein the major and the minorspokes are made of 17-4 pH stainless steel.
 17. An apparatus forprocessing a material, wherein gel stalactites are formed in thematerial, comprising:(a) an agitator section having a bottom and anoutlet adjacent the bottom thereof; (b) a transfer screw attached to theagitator section; (c) a spiral ribbon extending upwardly from thetransfer screw and attached thereto; (d) a ring disposed verticallyabove the spiral ribbon and connected thereto; (e) a plurality of majorspokes extending between the ring and the transfer screw; (f) aplurality of minor spokes extending between the spiral ribbon and thetransfer screw; and (g) means for catching gel stalactites formed in thematerial baffle disposed vertically above the spiral ribbon andconnected to the major and minor spokes below the ring.